Electrospinning (electric charge induced spinning) is known as a method for producing filamentous (fibrous form) substances (nanofibers) made of polymeric substances or the like and having a diameter in a submicron scale.
In the electrospinning method, a solution, which is a raw material liquid prepared by dispersing or dissolving polymeric substances or the like in a solvent, is effused (ejected) into a space through a nozzle or the like, while charging the solution by applying an electric charge. The solution traveling in the space is electrically stretched, and nanofibers are thus produced.
Following describes the electrospinning method more specifically. The solution which is electrically charged and effused into the space gradually loses solvent through evaporation while traveling in the space. With this, volume of the traveling solution gradually decreases. On the other hand, the electric charge applied to the solution remains in the solution. As a result, charge density of the solution traveling in the space gradually increases. Since the solvent continuously evaporates, the charge density of the solution further increases. When Coulomb force, which is generated in the solution and acts oppositely, exceeds the surface tension of the solution, the solution undergoes a phenomenon in which the polymer solution is explosively stretched into filament (hereinafter referred to as the electrostatic stretching phenomenon). Such electrostatic stretching phenomenon repeatedly occurs at an exponential rate in the space, thereby producing nanofibers made of polymeric substances with a submicron diameter.
When the electrospinning method thus described is adopted, it is possible to increase a yield of the nanofibers by effusing a large amount of the solution into the space. However, for example, when many nozzles are arranged as the device described in Patent Literature (PTL) 1, a problem occurs. For example, potential of the nozzles to which a high voltage is applied does not stabilize, and nanofibers are produced only from a part of the solution effused into the space. In view of this, by rotating a cylindrical-container like effusing body, which is for effusing the solution, and causing the solution to be effused from holes, which are circumferentially provided on the effusing body, by centrifugal force, the inventors of the present invention successfully effused a large amount of the solution. In addition, the inventors have confirmed that electrostatic stretching phenomenon is observed for most of the large amount of solution effused, and nanofibers are produced. In addition, to charge the solution, which is effused into the space by the centrifugal force, electric charge needs to be supplied to the solution via the effusing body which rotates. In view of this, the inventors adopt a structure in which a brush attachable to a motor contacts the effusing body so that electric charge is supplied to the solution.